A cellular telecommunications system is a communication system that is based on use of radio access entities and/or wireless service areas. The access entities are typically referred to as cells. Examples of cellular telecommunications systems include standards such as the GSM (Global System for Mobile communications) or various GSM based systems (such as GPRS: General Packet Radio Service), AMPS (American Mobile Phone System), DAMPS (Digital AMPS), WCDMA (Wideband Code Division Multiple Access), TDMA/CDMA (Time Division Multiple Access/Code Division Multiple Access) in UMTS (Universal Mobile Telecommunications System), IMT 2000, i-Phone and so on.
In a cellular system, a base transceiver station (BTS) provides a wireless communication facility that serves mobile stations (MS) or similar wireless user equipment (UE) via an air or radio interface within the coverage area of the cell. As the approximate size and the shape of the cell is known, it is possible to associate the cell to a geographical area. The size and shape of the cells may vary from cell to cell. Several cells may also be grouped together to form a larger service area. A base station may provide more than one cell. Each of the cells can be controlled by an appropriate controller apparatus. For example, in the WCDMA radio access network the base station (which may be referred to as Node B) is connected to and controlled by the radio network controller (RNC). In the GSM radio network the base station may be connected to and controlled by a base station controller (BSC) of a base station subsystem (BSS). The BSC/RNC may be then connected to and controlled by a mobile switching center (MSC). Other controller nodes may also be provided, such as a serving GPRS support node (SGSN). The MSCs of a cellular network are typically interconnected and there may be one or more gateway nodes connecting the cellular network e.g. to a public switched telephone network (PSTN) and other telecommunication networks such as to the Internet and/or other packet switched networks.
The cellular network apparatus and/or the mobile station can be employed for provision of location information of the mobile station and thus the user thereof. More particularly, the cells or similar geographically limited service areas and associated controller nodes facilitate the cellular telecommunications system to produce at least a rough location information estimate concerning the current geographical location of a particular mobile station. If the location of the cell is known, it is possible to conclude therefrom the geographical area in which the given mobile station (communicating in said cell) is likely to be at a given moment. This information may be provided also when the mobile station is located within the coverage area of a visited or “foreign” network. The visited network may be capable of transmitting location information of the mobile station back to the home network, e.g. to support location services or for the purposes of call routing and charging.
A mobile station may be provided with appropriate equipment to provide information on which the positioning of the mobile station can be based on. The mobile station may communicate the information via the base to an appropriate network element that may use the information in a predefined manner.
More accurate location information may be obtained based on various location estimation methods, e.g. based range difference (RD) measurements or by means of a global positioning system (GPS). The measurements may be accomplished at the mobile station or by a number base stations.
A location service functionality may be provided by a separate network element such as a location server which receives location information from the telecommunications system. If no further computations and/or approximations are made, this would give the location to an accuracy of one cell, i.e. it would indicate that the mobile station is (or at least was) within the coverage area of a certain cell.
3GPP specification 3GTS 23.032 v3.1.1 (2000-3) titled ‘Universal Geographical Area Description’ presents a possibility for defining geographical areas. The definition is based on shape and one or several location points. This concept may be referred to as DEfined Geographical Areas (DEGA). Based on this concept the mobile station measures its position. The station is adapted to compare the determined position to a defined geographical area. If it is determined that the mobile station has entered the defined area, the mobile station sends a notification thereof to the network. Information that is required for the area definition is stored at the mobile station. The DEGA information may be broadcast via the base stations to the mobile stations. The DEGA information may also be stored beforehand in a SIM/USIM (subscriber identity module/UMTS SIM) of the mobile station. The DEGA information typically consists of one or several geographical points and shapes as defined by the 3GTS 23.032 specification. The DEGA information may also include a unique name, identification number of other identifier for the defined area in question.
It might be useful for various commercial and non-commercial services and similar applications to have information concerning mobile stations that are located within a particular defined geographical area. In some applications it might be useful for the network element to be able to accomplish the operation for obtaining location information only in selected parts of the communication system. There are also applications where it might be useful to be able to locate selected mobile stations or subscribers in a defined area. For example, various organisations or even individuals may want to send information and/or offer services to mobile stations only in a particular defined geographic area and/or to certain type of subscribers in a particular geographical area. The mobile stations in a certain area and/or certain types of subscribers may also need to be tracked e.g. for fleet management purposes. There may also be a need for a quick provision of the location information. It may also be advantageous if the location information could be provided without causing excessive load into the resources of the communication network.